So far we neither specified the form in which the function \(\phi \)  is given to the algorithm, nor provided any special properties of \(\phi \) . As we will see, variants of GD-FixedPoint capture the class \(\)  and the problem KKT[1]} also consider a problem that they call KKT which corresponds to the most general variant of GD-FixedPoint. They leave as an open problem the computational complexity of [2]}'s (explicit) KKT, which we settle in this paper. that have been defined in [2]}.
